Traveling wave type tube and method of manufacture



June 28, 1960. B. KLEINMAN TRAVELING WAVE TYPE TUBE AND METHOD OF MANUFACTURE Filed April 1l. 1958 INVENTOR lllllllllllllllllllllll l. nl! x BERNARD KLEINMAN United States Patent TRAVELING WAVE TYPE TUBE AND METHOD or MANUEACTURE Bernard Kleinman, New York, N.Y., assignor to Radio Corporation of America, a corporation of Delaware Filed Apr. 11, 1958, Ser. No. 727,955

'6 Claims. (Cl. S15-"3.5)

orderto achieve amplification of the signal waves. The f Y` delay` line, which isusually in the form ofa Irelatively long, -slender conductive helix, must be rigidly supported `to achieve close adjacencyA between the beam and the line. To this end the helix is usually either (1) mounted in va snug fit within an elongated, non-conductive'envelope or, (2) supported in coaxial spaced relation with respect to the envelope by means of three equally spaced Yinsulating rods positioned around the helix. However, such helix support arrangements have severaldisadvantages. For example, in the first named arrangement the ,close fit required between the helix 'and theenvelope sometimes results in fabricatingdiiculties `and breakage of the usually fragile envelope. In addition, the dielectric loading of the helix is very high.. f

Bianculli Patent 2,806,170 relates to a form of moun ing the helix, according the the second arrangement mentioned above, in which the helix andv ceramic rodsare assembled together within the envelope by means of clamp'n'ngs and resilient members which are disposed between the rods and the clamp rings and resiliently press the rods against the helix. Y f f .An object of the presentinvention is to providean. improved resilient clamping means in the Bianeulli type of helix-rod assembly.

A further object is to provide a novel method of mounting a helix assembly within the envelope of a traveling wave type tube. Y

The foregoing and other objects are Iachieved in accordance with the method of the invention by providing a resilient tubular metallic clamp which is to be clamped .about an assembly of support rods yarrayed about a helix. This clamp is initially circular with a cross sectional area which is greater than that of the helix assembly to be inserted therein but with a normal diameter which is less than that of the circle circumscribing said helix assembly. To produce the clamped assembly, the clampv is -tirst .distorted by yforces applied at a number of points corresponding to the number of rods so as to produce ageometrical confguration more nearly identical ,to that of the assembly rods and helix. The rods and helix are inserted into the distorted clamp with the rods intermediate the points of application of the forces, Upon removalof vthe distorting forces, the clamp restores itself :1o-'nearly its original circular shape, and in doing so compresses the reds `and :helix into a rigid assembly.

2,943,228 Patented June 28, ,1.969

.ICC

Preferably, more than one clamp is used so that the helix is supported along a substantial part of its length.

yIn the drawing:

Fig. l1 is a partially cut away longitudinal sectional 5 view of a traveling wave type tube embodying the invention;

Fig. 2 is a transverse sectional view taken on line l2-.12 of Fig. 1;

Fig. 3 is a transverse View of a resilient member vand a helix sub-assembly supported in a clamping structure' used in practicing the method'of the invention; ,t

Fig. 4 is a partially cut-away longitudinal A sectional view of a traveling wave type tube embodying @Other form of the invention; and

Fig. 5 is a transyerse sectional View .taken on line`r ofF-igml., Y K The traveling wavev type tube shown in Figs, l and 2 is .known as .a backward wave oscillator and .comprises ya tubular glassenvelo'pe 10 of circular .crosssection lcontainingan electron g'un 12at one end of the tube, a

collector electrode 14 at the opposite. end .of the tube, and a .conductive helix or Vhelical conductor `16 inter.

mediate the electron gun 12 and the collector electrode 14; Thestructural and operational details VofV theuele- Y v trfon gun 12 and the collector electrode 14 are well understood and will therefore not be further describ.edexcept to note that they should be designed -to project and col- Ilect an electron beam along the, axis of the tube.

The helix 16 is mounted coaxially withV-the'renvelope 10 between three insulating rodsf18, ofglass orcerarnic,

` for example, extending klongitudinally insidethe envelope/ :10 parallel to the common axis of therenvelope 1 1o and the helix 16. The helix is .maintained in @lealtad Y -axial alignment With-the electron gung12 and thegB-.COl-

lector. electrode 14 by means ofptubular projections 20 and22 of, `respectively,the electron gun 12 and collectorl VVi electrode 14 and by a plurality of resilientmetallic tubular clamps or sleeves 24 ,and'26V according to the inven- ;tion, the clamps being described in vdetail below. TheY 4 .40 -end portions of each insulating' rod 1,8.gare disposed around and .snugly engagethe tubulai-` projectigins..2,0

and 2,2.and are fixed in position with respect to the pro-v i' jections 20 and 22 by :means ofthe clampsY .24- and 26,

.which cause the insulating rods18 to gripthe projections 4520 `and 22. The helix 16.7,is adapted to be coupledvto 'A fr f an external load by means ofan antenna .conductor extension23 and a coupling sleeve'25. v The' method of force' fitting the clamps 24 and -256 around the insulating4 rods 18 Vis illustrated in ,Fig.3. A suitable clamping fixture `28 having `an overall length -generally the same as the helix 16 and insulating rods 18 vis made up of a U-shaped base 30'and four .upstanding supports 32 mounted on the legs of the U, there being two supports 32 at each end of the base. A horizontal pressure plate 34 is slidably mounted across the tops of the supports 32, with the supports 32 protruding through holes in the plate 3.4 so that the plate 34 can be moved up or down.

In carrying out the method of the invention, two metal rods 36 are first placed in the corners ofthe U-shaped base 30. The clamps 24 and 26 are placed on the metal rods 36 and spaced lapart to conform to the position they will assume in the finished tube. A third metal rod 36 is placed onv top of the clamps andthe plate `34 is brought into contact with ghis rod '36;Y The underside vof, ,the plate 34. has a, notch 38 therein to contain. `the .third rod 36. The rods 36 and base .0.are suitably `disulating rods 18 disposed around the helix 4 and insulating rod 18 sub-assembly, outline in Fig. 3. V24', 26 is such that the elastic limit of the clamp metal 'is not exceeded. Suitable high-tensile strength metal,

mensioned so` that the rods 36 are clamps 24 and 26V at equal intervals, in this case 120 apart.

Prior to the application of force on the plate 34, the

clamps 24, 26 have -a circular cross section such thatV their inside diameter is slightly less than the diameter of the circle delined by the outer extremities of the in- 16. Stated differently, the transverse extent of the inside surfaces of the clamps 2,4, 26 is less than the transverse extent of the generally triangular figure bounded by the insulating rods 18, but the circular area detined by the inside surfacesY of the clamps 24, 26 is greater than the area of 'said generally triangular ligure.

Downward force applied to the plate 34 is transmitted through the equally spaced metal rods 36 to the points `of the clamps 24, 26 in contact with the metal rods 36. `These points are flexed inwardly,

but the portions of the clamps lying midway between lthe metal rods 36 are bowed outwardly, so as -to distort the clamps 24, 26 into a shape which more nearly conforms to, but is of greater size than, the triangular shape of the helix 16 as shown lin dotted The force applied to the clamps such assteel, may be used for the clamps.

While the clamps 24, 26 are thus distorted, the subassembly of helix 16 and insulating rods 18, supported on suitable mandrel, is inserted within the clamps 24,

'26,with the bowed out portions thereof providing suin doing so clamp the insulating rods `18 to compress them against the helix 16 into a rigid sub-assembly. ln

addition, the ends of the insulating rods 18 are comarrayed about the l pressed about the projections 20, 22 to fix them in posi- Thereafter, the assembled elements are sealed vacuum tight with the glass envelope 10.

`It is noteworthy `that the method of assembling tube elements accordingto the invention as above described `is characterized byits simplicity, because of the lack "of any of the more Vcumbersome means for joining parts, 'such as'welds, brazes, or otherV metal flow processes. Practically all the elements are held in fixed relation with each other solely by compression forces.

Figs; 4 and 5 show a traveling wave type amplifier y tube provided with clamps which constrain the helix subassembly according to the invention and which serve `also as parts of the envelope structure. in this embodiment, the envelope comprises three resilient metallic tubular clamps 40, 42, 44, joined end-to-end to two intermediate insulating rings 46, 48, which may be ceramic,

by brazing. The central clamp 42 is rather long and surrounds the length of the helix 50 except for a few turns at each end of the helix 50. These few turns of the helix 50 are surrounded, with some clearance, by the ceramic rings 46, 48, which serve as dielectric windows to permit the introduction and extraction respectively of electromagnetic energy into and from the helix 50.

In accordance with the invention, the long central 1 `clamp 42 is clamped around the major central portion Vof the insulating rods 52. The two shorter clamps 40,

44 are clamped around the ends of the insulating rods 52. The ends of the rods 52 in turn are clamped about projections 54, 56 of the electron gun 58 and collector 60, respectively. Two antenna conductors 62, 64 are connected between the ends of the helix 50`and the ends of the central clamp 42.

In fabricating the tube structure of Figs. 4 and 5, ceramic rings 46, 48 and metal clamps 40, 42, 44 are assembled end to end with each clamp being held in a fixture of lthe kind shown in Fig. 3. The clamps 40, 42, 44 are then distorted in the manner previously described, the helix 50 and insulating rods 52 inserted within the clamps and ceramic rings 46, 48, and upon removal of the distorting force, the clamps 40, 42, 44 compress about the helix assembly. The helix assembly is then removed from the fixtures, and the clamps 40, 42, 44 and ceramic rings 46, 48 are brazed together. Tubular envelope portion 66 and collector 60 are then sealed to the clamps 40 and 44 at the ends of the tube to complete the envelope assembly.

What is claimed is:

l. An electron discharge device comprising an envelope including a resilient tubular metallic portion, and a substantially rigid elongated polygonal conductive helix subassembly disposed within said envelope portion, said envelope portion encircling, engaging and clamping said helix sub-assembly into a rigid assembly therewith.

' 2. An electron discharge device of the traveling wave type comprising an envelope including a resilient tubular metallic portion, an elongated conductive helix within said envelope portion, and an array of mutually spaced insulating rods surrounding and engaging said helix, said envelope portion encircling, engaging and compressing said rods against said helix.

f 3. A method of making a helix assembly, including the steps of providing an elongated substantially rigid sub-assembly of a helix surrounded by an array ofnlutually-spaced longitudinally-extending support rods engaging said helix in a predetermined non-circular configuration, providing a resilient tubular metallic member normally shaped to have a cross-sectional area greater than but a transverse extent less than said configuration, applying force to distort said resilient member within its elastic limit to increase and decrease its transverse extent in different portions thereof and make it conform more nearly toV said configuration, inserting said subassembly within said distorted member, and removing said force thus permitting said tubular member to be re- -stored nearly to its original shape and brought into Vwithin its elastic limit for increasing the inside transverse extent of said envelope portion along certain portions thereof and decreasing the inside transverse extent along other portions, inserting a substantially rigid -elongated polygonal conductive helix assembly having large and small transverse dimensions within said envelope portion with the large dimensions of said assembly fitting within said certain portions of increased inside transverse extent and the small dimensions tting within Vsaid other portions, and then removing said force thereby permitting said envelope portion to restore itself and engage and clamp said assembly into a unitary structure with said portion.

5. The method described in claim 4 and wherein said helix assembly comprises an elongated conductive helix and a plurality of insulating rods external to and engaging said helix longitudinally thereof, and wherein each of said rods is disposed within one of the enlarged transverse extents of said envelope portion.

6. A method of making helix assembly, including the steps of xing a resilient tubular metallic member within a support structure, subjecting said member to distortion force within its elastic limit for increasing the inside transverse extent of said member along certain portions thereof and decreasing the inside transverse extent along other portions, inserting a substantially rigid elongated References Cited in the ie of this pi UNITED STATES PATENTS Best Apr.' 19, 1955 Glenn et al. June 26, 1956 Bianculli Sept. 10, 1957 Johnson Sept. 17, 1957 McBee Aug. 19, 1958 

